The invention relates to a novel process for preparing 2,4-disubstituted thiophene-3-sulfonyl isocyanates which are described as intermediates for active ingredients in agriculture, especially for substituted herbicidally active thienylaminocarbonyltriazolinones (cf. WO 01/05788) and sulfonylureas (WO 01/10863). 2. Description of Related Art
It is known that certain substituted thienylsulfonyl isocyanates can be prepared by phosgenation in the presence of organic bases, in particular the base DABCO, from the corresponding sulfonamides (EP-A 30 142, U.S. Pat. No. 4,481,029). However, a disadvantage of this process is that an expensive organic base has to be used.